Reciprocating switch mechanism with improved thumbwheel actuator including rack and pinion structure

ABSTRACT

A slide is movable lengthwise of a housing to move contact means therein along conducting means. Secured to the housing is a stationary rack bar that is longer than the housing and supports a carrier movable along the bar. A rack bar, which is movable lengthwise along the stationary bar and carrier, is connected with the slide for moving it. Rotatably mounted on the carrier is a pair of rigidly connected coaxial gears, one of which is smaller than the other. The large gear meshes with the stationary rack bar and the smaller gear meshes with the movable rack bar. When the gears are rotated, the one engaging the stationary bar will move the carrier along the bar, and the other gear will move the movable bar along the stationary bar a shorter distance than the carrier moves so that the slide will be moved only the shorter distance.

United States Patent [151 3,639,706 Purdy Feb. 1, 1972 [54]RECIPROCATING SWITCH 2,577,955 12/1951 Dixon ..200/l6 F MECHANISM WITHIMPROVED 2,931,866 4;!960 Brown ...200/l6 F 3,047,683 7 i962 Shlesinger,.ll'. 200/153 P INCLUDING RACK AND PINION Helus et al "200/16 FSTRUCTURE Harold L. Purdy, Hummelstown, Pa.

Stackpoie Carbon Company, St. Mary's, Pa.

Mar. 15, 1971 Inventor:

Assignee:

Filed:

Appl. No.:

US. Cl. ..200/l7 R, 200/16 F, 200/153 P, 74/422 Int. Cl ..H0lh 3/08,HOlh 15/16 Field of Search ..200/16 F, i7, 153 P; 74/1039, 74/29, 30,422

References Cited UNITED STATES PATENTS Van Vleck ..200/l6 F Scott..2()()/l6 F Burns, .lr. ..200/l 7 R Primary Examiner-J. R. ScottAttorney-Brown, Murray, Flick & Peckham [5 7] ABSTRACT A slide ismovable lengthwise of a housing to move contact means therein alongconducting means. Secured to the housing is a stationary rack bar thatis longer than the housing and supports a carrier movable along the bar.A rack bar, which is movable lengthwise along the stationary bar andcarrier, is connected with the slide for moving it. Rotatably mounted onthe carrier is a pair of rigidly connected coaxial gears, one of whichis smaller than the other. The large gear meshes with the stationaryrack bar and the smaller gear meshes with the movable rack bar. When thegears are rotated, the one engaging the stationary bar will move thecarrier along the bar, and the other gear will move the movable baralong the stationary bar a shorter distance than the carrier moves sothat the slide will be moved only the shorter distance.

8 Claims, 7 Drawing Figures PATENTEU FEB H972 I 3.639.706

sum 2 or 3 ATTOR/VEKS.

PAYENTED FEB H97? 3.839.706

sum 3 or 3 "5' 7 m/n-Wro/a.

#42040 L. Pl/ROY ATTORNEYS.

RECIPROCATING SWITCH MECHANISM WITH IMPROVED THUMBWIIEEL ACTUATORINCLUDING RACK AND PINION STRUCTURE In linear motion electricalcontrols, such as potentiometers for example, it often is desirable tobe able to make either a coarse adjustment or a fine adjustment. Variousideas have been advanced for doing this, but they do not always produceas fine adjustments as desired.

It is among the objects of this invention to provide a linear motionelectrical control, the adjustment of which can be changed rapidly or toa very slight extent in an easy manner.

The preferred embodiment of the invention is illustrated in theaccompanying drawings, in which FIG. 1 is a plan view;

FIG. 2 is a side view;

FIG. 3 is an end view;

FIG. 4 is an enlarged fragmentary longitudinal section taken onthe lineIVIV of FIG. 1;

FIG. 5 is an enlarged cross section taken on the line VV of FIG. 2;

FIG. 6 is an enlarged fragmentary longitudinal section taken on the lineVIVI of FIG. 1; and

FIG. 7 is a cross section taken on the line VII-VII of FIG. 6.

Referring to FIGS. 2, 6 and 7 of the drawings, the case 1 of theelectrical control, which will be considered herein to be apotentiometer although the invention is not limited to such a device butcould be a switch or the like, is long in comparison with its height andwidth. Inside the case there are spaced resistance and collectorelements 2 and 3 provided with suitable terminals 4 extending out of theback or bottom of the case. The front or top of the case is providedwith a central longitudinal slot 5, through which a slide 6 extends. Theslide overlaps the upper and lower surfaces of the top wall of the caseso that it can move only lengthwise of the slot. Inside the case theslide carries contact means, such as a wire coil 7, that forms abridging contact engaging the resistance and collector elements.

Disposed above the case and secured to it is a rack bar 9 that isconsiderably longer than the case. It extends away from at least one endof the case, preferably both ends. It may be connected to the case invarious ways. One way is by tongues 10 struck out of the bar andextending through holes in the upper ends of brackets 11 mounted on theopposite ends of the case. The brackets are clamped between the bar andtongues. The brackets may be designed to be inserted in a printedcircuit board or a panel to support the control.

The rack bar is channel shape, as shown in FIGS. 5 and 7. The upper edgeof one of its side flanges is cut to form a row of rack teeth I3. Theupper edge portion of the opposite flange is turned inwardly parallel tothe base of the channel to form a lip 14 that projects into a slot 15 onone side of a carrier 16. The toothed flange of the channel fits inlongitudinally spaced notches 17 in the bottom of the carrier and thelatter has inwardly projecting ledges l8 engaging the bottom of thechannel. Consequently, the carrier is secured to the rack bar and canmove only lengthwise of it. The ends of the toothed flange may be cutand bent outwardly to form stops 19 (FIGS. 1 and 3) that will preventthe carrier from leaving the ends of the bar.

The bottom of the carrier inside the channel is provided with alongitudinal passage, in which a movable rack bar 21 is slidablymounted. One side of the passage is formed in part by a pair ofdownwardly extending lugs 22 that engage the inner surface of thetoothed flange of the stationary rack bar and extend laterally beneaththe movable rack bar to support it as shown in FIG. 5. The upper surfaceof the movable bar is provided with a row of teeth. One end of this baris secured to the slide, such as by a lateral fork 23 straddling andtightly engaging the projecting portion of the slide, as shown in FIGS.1, 6 and 7. The central portion of the carrier above the movable rackbar is provided with a recess 24 that is open at the top and at the sideof the carrier opposite to its lateral slot I5. In

this recess a stationary horizontal pin 25 is joined at one end to thecarrier. The pin projects from the open side of the recess. Rotatablymounted on the pin are two gears that are rigidly connected together.

The inner gear 27 has a smaller diameter than the other gear 28 andmeshes with the movable rack 21, although with a different arrangementof the movable rack bar the sizes of the gears could be reversed. Theouter gear meshes with the teeth 13 along the adjoining flange of thestationary rack bar. It is desirable to also mount a thumb wheel29 onthe outer end of the pin, the wheel being rigidly connected to the gearsso that all will turn in unison. The thumb wheel has a greater diameterthan the gears. A knob 30 may be mounted on the carrier in any suitablemanner, such as by providing the carrier with upwardly projecting prongs31 (FIG. 4) that fit in holes in the bottom of the knob. The knob isprovided in its top with a recess 32 having a slot 33 through itsbottom. The thumb wheel projects up through the slot into the recess sothat it can be turned by a thumb or finger, or the knob can be graspedto move the carrier without touching the thumb wheel.

The control can be adjusted by moving the carrier 16, by means of itsknob 30, along the stationary rack bar, which will cause the large gearto roll along that bar and thereby turn the small gear. Since the smallgear is moved along the stationary rack by the carrier at the same timethat the small gear is being turned by the larger gear, the small gearpushes the movable rack bar 21 along the stationary rack bar in the samedirection the carrier is moving. However, due to the smaller diameter ofthe small gear, it simultaneously compels the movable rack bar to movein the opposite direction, so that the movable bar travels along thestationary bar a shorter distance than the carrier. This means that theslide 6, which is controlled by the movable rack bar through fork 23,moves slowly as compared with the carrier and therefore a shorterdistance. The distance the slide is moved for any given movement of theknob is determined by the relation of the pitch diameters of the twogears. If they were both the same size, they would merely roll togetheralong both rack bars without moving the movable bar and therefore theslide would stand still. Consequently, the closer the pitch diameter ofthe small gear approaches the pitch diameter of the large one, withoutbecoming the same diameter, the slower the movable rack will be moved.It will be seen that while the knob 30 is being moved a considerabledistance, the slide may be moved only a small amount, which makes fineadjustment of a potentiometer or other control very easy. If gear 27were larger than gear 28, the movable rack would be moved in thedirection opposite to that of the knob.

Extremely fine adjustment is obtained by not using the knob to move thecarrier, but by turning the thumb wheel 29. Since the wheel is largerthan the large gear, the gear will roll along the stationary rack adistance shorter than the distance a point on the periphery of the wheelmoves while the wheel is being turned. In other words, the periphery ofthe large gear will turn more slowly than the periphery of the wheel.The still more slowly turning small gear, as before, will slowly movethe movable rack and the slide 6 ahead. Consequently, for a few degreesof rotation of the wheel, the slide may be moved an almost imperceptibledistance.

The electrical control described herein has several advantages. Withdifferent gear ratios, the distance the knob needs to move in order tomove the control slide its full distance can be varied. The knob can bemoved rapidly, but the control will be adjusted slowly. One straightmovement of the knob can give the desired adjustment, in place ofrepeated rotations of a knob on a rotatable control. Of course, theextremely fine adjusting is an important feature. When the control is aswitch, extremely short step-by-step travel can be obtained, the limitbeing a matter of tolerances and not human dexterity and patience.Because of the long stroke of the knob, direct dial indication can beused. The high ratio between knob and slide movements is effectedwithout the use of tiny parts, so the control can be rugged andreliable, manufactured at reasonable cost, and have a long life. Thesize of the control is small for its length of travel, so little chassissurface is taken up by the mounting. During coarse tuning, the gear andthumb wheel assembly acts like a flywheel, which gives a better feelingto the action. By using noncircular gears and racks to match them, itwould be possible to produce various knob to movable rack travel ratios.That would allow, for example, certain parts of the control to be morefinely tuned than others and permit passing through other portionsrapidly.

. According to the provisions of the patent statutes, I have explainedthe principle of my invention and have illustrated and described what Inow consider to represent its best embodiment. However, I desire to haveit understood that, within the scope of the appended claims, theinvention may be practiced otherwise than as specifically illustratedand described.

Iclaim:

l. A linear motion electrical control comprising an elongated case,electrical conducting means in the case, a slide movable lengthwise ofthe case, contact means in the case movable by the slide along saidconducting means, a stationary rack bar secured to the case andextending away from at least one end of it, a carrier mounted on the barfor movement lengthwise thereof, a rack bar movable lengthwise along thestationary bar and carrier, means connecting the movable bar with theslide, and a pair of connected coaxial gears rotatably mounted on thecarrier on an axis transverse thereto, one of the gears being smallerthan the other and each meshing with one of the rack bars, one of thegears being rotatable to move the carrier and movable bar along thestationary bar, whereby the other gear will move the movable bar alongthe stationary bar at a different speed than the carrier moves.

2. A linear motion electrical control according to claim 1, including athumb wheel coaxial with said gears and rigidly connected therewith forrotating them, said wheel being larger than said gears.

3. A linear motion electrical control according to claim 1,

including a thumb wheel coaxial with said gears and rigidly connectedtherewith for rotating them, said wheel being larger than said gears,and a knob mounted on said carrier for moving it along the stationaryrack bar, the knob being provided with a slot through which a portion ofthe thumb wheel projects.

4. A linear motion electrical control according to claim I, in

which said stationary rack bar is in the form of a channel having sideflanges, one of said flanges being provided with the teeth of the rackand the other flange having a lip along its outer edge projecting towardthe toothed flange, and said carrier having slots receiving said lip andtoothed flange to hold the carrier on the stationary bar.

5. A linear motion electrical control according to claim 1, in whichsaid stationary rack bar is in the form of a channel having sideflanges, one of said flanges being provided with the teeth of the rackand the other flange having a lip along its outer edge projecting towardthe toothed flange, and said carrier having slots receiving said lip andtoothed flange to hold the carrier on the stationary bar, said movablerack bar being located between said flanges and parallel thereto, andsaid carrier having a guideway therethrough receiving the movable bar.

6. A linear motion electrical control according to claim 1, in whichsaid housing and stationary rack bar are provided with registeringlongitudinal slots, said slide extends through said slots, and saidmovable rack bar is disposed beside said slots at the side of thestationary bar opposite said housing.

7. A linear motion electrical control according to claim 1, in whichsaid carrier is provided with a pin extending transversely of said bars,and said gears are rotatably mounted on said pm.

8. A linear motion electrical control according to claim 1, in whichsaid large gear meshes with the stationary rack bar and the small gearmeshes with the movable rack bar.

1. A linear motion electrical control comprising an elongated case,electrical conducting means in the case, a slide movable lengthwise ofthe case, contact means in the case movable by the slide along saidconducting means, a stationary rack bar secured to the case andextending away from at least one end of it, a carrier mounted on the barfor movement lengthwise thereof, a rack bar movable lengthwise along thestationary bar and carrier, means connecting the movable bar with theslide, and a pair of connected coaxial gears rotatably mounted on thecarrier on an axis transverse thereto, one of the gears being smallerthan the other and each meshing with one of the rack bars, one of thegears being rotatable to move the carrier and movable bar along thestationary bar, whereby the other gear will move the movable bar alongthe stationary bar at a different speed than the carrier moves.
 2. Alinear motion electrical control according to claim 1, including a thumbwheel coaxial with said gears and rigidly connected therewith forrotating them, said wheel being larger than said gears.
 3. A linearmotion electrical control according to clAim 1, including a thumb wheelcoaxial with said gears and rigidly connected therewith for rotatingthem, said wheel being larger than said gears, and a knob mounted onsaid carrier for moving it along the stationary rack bar, the knob beingprovided with a slot through which a portion of the thumb wheelprojects.
 4. A linear motion electrical control according to claim 1, inwhich said stationary rack bar is in the form of a channel having sideflanges, one of said flanges being provided with the teeth of the rackand the other flange having a lip along its outer edge projecting towardthe toothed flange, and said carrier having slots receiving said lip andtoothed flange to hold the carrier on the stationary bar.
 5. A linearmotion electrical control according to claim 1, in which said stationaryrack bar is in the form of a channel having side flanges, one of saidflanges being provided with the teeth of the rack and the other flangehaving a lip along its outer edge projecting toward the toothed flange,and said carrier having slots receiving said lip and toothed flange tohold the carrier on the stationary bar, said movable rack bar beinglocated between said flanges and parallel thereto, and said carrierhaving a guideway therethrough receiving the movable bar.
 6. A linearmotion electrical control according to claim 1, in which said housingand stationary rack bar are provided with registering longitudinalslots, said slide extends through said slots, and said movable rack baris disposed beside said slots at the side of the stationary bar oppositesaid housing.
 7. A linear motion electrical control according to claim1, in which said carrier is provided with a pin extending transverselyof said bars, and said gears are rotatably mounted on said pin.
 8. Alinear motion electrical control according to claim 1, in which saidlarge gear meshes with the stationary rack bar and the small gear mesheswith the movable rack bar.